From the time series on previous pages, it appears that Cardiff is a consistent outlier in terms of its population density. The boxplot here appears to confirm this. To formally identify the outlier, utilise an outlier analysis, using Quartile 3 + (1.5 * IQR)
[1] 1409.14
The above output is the resulting threshold of the outlier analysis. (1409.14) is the outlier threshold for the Welsh population densities in 2016. Any local authority with a population density higher than this threshold is formally labelled an outlier and should be removed from Pearson’s correlation coefficient.
local_authority Population.density mean_year
1 Cardiff 2563.33 2016
As can be seen above, the only local authority with an outlier population density is Cardiff. Cardiff’s population density is over 80% larger than the outlier threshold. Therefore, it can be removed from Pearson’s correlation test.
[1] -0.6714913
In removing Cardiff from the analysis, we have identified a strong negative association between life expectancy and population density. The threshold used to assume a strong negative correlation is -0.5. Below, the coefficients of the same analysis for the other demographics within the data are presented.
[1] -0.6986888
Interestingly, the data for males returns a stronger negative association than in the female data.
[1] -0.6327204
For 65 year old females, there is a slightly weaker negative association between life expectancy and population density. However, this value is still well above the 0.5 threshold used to denote a strong association.
[1] -0.7643989
Of all the demographics analysed, the 65 year old males’ life expectancy shows the strongest negative association with population density.
source = Data Cymru Correct as 03/11/2019
source = Stats Wales Correct as 03/11/2019
Please visit the source data websites to see their associated metadata.
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